RSP Crew

So, how long does a hot water system take to heat up? We know it’s frustrating to wait, especially if you think something might have gone wrong with your expensive unit that you rely on each day for showers and baths. Perhaps you’re browsing for a new system and want to know what to expect, like if you’re tossing up between a tankless vs a traditional tank system, or perhaps even a state-of-the-art heat pump. Or maybe you’re just curious.

Whatever brought you here, this guide covers everything you need to know about hot water heating times, from quick reference tables to in-depth troubleshooting for when things aren’t working as they should.

Hot Water Heating Times at a Glance

Before we dive into the details, here’s a quick reference table showing typical heating times for different hot water system types. Keep in mind these are averages for systems in good working condition.

System Type	Typical Heating Time	Best For
Gas Storage Tank	30-60 minutes	Families wanting faster recovery
Electric Storage Tank	1-3 hours	Homes with off-peak tariffs
Gas Instantaneous	5-15 seconds	Unlimited hot water on demand
Electric Instantaneous	5-10 seconds	Small households, limited space
Heat Pump	2-6 hours	Energy-conscious households
Solar (with booster)	1-5 hours	Eco-friendly homes in sunny areas

These times assume you’re heating water from cold (around 20°C) to the standard storage temperature of 60°C. If your system is taking significantly longer than these benchmarks, something might need attention.

How Long Does It Take for a Hot Water Tank to Heat Up?

First, let’s do some troubleshooting. We know you’re shivering in the bathroom waiting for that freezing cold water to heat up, so let’s see what’s going on whilst pondering the question: how long does it take for hot water to heat up?

Troubleshooting Hot Water System Heat-Up Delays

1. Check power sources

Is your system even connected to its power source? If it’s electric, that means checking the circuit breakers. And for gas systems? How long does a gas water heater take to heat up? A bit faster than electric, but let’s start by peering into the system to look for the presence of that pilot light.

2. Inspect thermostat settings

Next, verify that the thermostat is set to an appropriate temperature. If it’s set too low, it’s not going to be hot enough. However, your system should be set to a standard, regulatory-compliant temperature of 60°C for storage systems.

3. Evaluate tank capacity vs. usage

Do you have a tank-based system? If you do, perhaps you’ve just run out of water. If the stored water is all gone, your system won’t be able to catch up as you stand there waiting for it. This leads to the question of understanding recovery time versus initial heating, which we’ll cover shortly.

4. Look for leaks

Put your clothes back on and head outside to your system. Do you see your hot water system leaking badly? A few drops here and there from the pressure relief valve are normal, but something very soggy could be a major problem that needs immediate attention.

5. Could it be sediment build-up?

In storage systems, sediment accumulation at the bottom of that tank can act as a barrier to heat transfer. Over time, minerals from your water settle and insulate the heating element, making it work much harder to warm the water. It could be time for a flush.

6. Check for faulty heating elements

You might also need to look into whether your hot water system has a faulty heat element, especially if you’re asking “how long does an electric hot water system take to heat up?” This could be a key factor affecting the heating time of your system. For more detailed diagnostics, check our guide on electric hot water systems not working.

7. How old is your system?

If your system is past its prime, it may be struggling for heating efficiency. The average lifespan for electric hot water systems is 10-15 years, while gas systems typically last 8-12 years. Maybe that means waiting a little longer for water, or maybe it’s time to call the plumber. You can learn more about how long hot water systems last to help you decide.

How Tank Size Affects Heating Time

The size of your hot water tank plays a major role in how long you’ll be waiting. Larger tanks hold more water, which naturally takes longer to heat. Here’s what to expect based on common Australian tank sizes:

Tank Size	Electric Heating Time	Gas Heating Time
Small (50-100L)	45-90 minutes	20-30 minutes
Medium (125-180L)	1.5-2.5 hours	30-50 minutes
Large (250-315L)	2.5-4 hours	50-75 minutes
Extra Large (400L+)	4-6 hours	75-90 minutes

A common mistake is assuming you need the same size tank when upgrading systems. If you’re switching from gas to electric, or from a storage system to a heat pump, the heating characteristics change significantly. A 135L gas tank that served you well might not translate directly to a 135L heat pump, which heats more slowly and may need a larger capacity to meet the same demand.

How Long Does an Electric Hot Water System Take to Heat Up?

Storage-type electric hot water systems work by heating water in a tank and keeping it hot until needed. They use a heating element (similar to a kettle) to warm the water, and this process is naturally slower than gas combustion.

Typical electric storage heating times:

50L tank: 45-60 minutes
125L tank: 2-3 hours
160L tank: 2.5-3.5 hours
250L tank: 3-4 hours
315L tank: 4-5 hours

Factors affecting electric heating time:

Element wattage makes a difference. Systems with higher wattage heating elements (3.6kW vs 1.8kW) will heat water faster. Some larger tanks have dual elements, which can speed things up when both are functioning correctly.

Insulation quality matters too. Well-insulated tanks retain heat better, meaning less energy is wasted and recovery times are faster. Older tanks with degraded insulation may take noticeably longer.

If your electric system is taking longer than these benchmarks, the heating element may be coated with mineral deposits or could be failing altogether. A qualified plumber can test the element and replace it if needed.

How Long Does a Gas Hot Water System Take to Heat Up?

Gas storage systems heat water using a burner at the bottom of the tank, which is more powerful than an electric element. This means faster heating times overall.

Typical gas storage heating times:

90L tank: 20-30 minutes
135L tank: 30-45 minutes
170L tank: 40-60 minutes

Gas burns hotter than electricity can heat, which explains the speed advantage. For most systems, you’re looking at roughly half the heating time compared to an equivalent electric tank.

Factors affecting gas heating time:

Gas pressure and supply quality matter. If your gas supply is low or the pressure is inconsistent, it can slow down the heating process. Regular maintenance of your gas lines and ensuring your gas supply is reliable will help your system operate efficiently.

A dirty or partially blocked burner can also reduce heating efficiency. If you notice the flame isn’t as strong as it used to be, or if it’s yellow rather than blue, it’s time for a service.

The pilot light is another consideration. If it’s not burning properly or keeps going out, your system won’t heat efficiently. Modern systems with electronic ignition eliminate this issue, but older units may need occasional attention.

For gas hot water system services, it’s always best to work with a licensed gas fitter who can ensure everything is operating safely and efficiently.

How Long Does an Instantaneous Hot Water System Take to Heat Up?

Whether it’s running on electricity or gas, instantaneous (or tankless) hot water systems only heat water after you turn on the hot tap, with no storage tank in play at all. These systems are known for being energy-efficient, though they may have limitations in flow rate.

How long for a hot water system to heat up if it’s electric-instant?

The answer is in the name: pretty much instantly. We’re talking mere seconds, as long as it has power and is working at full steam.

Gas instant hot water systems also deliver hot water almost immediately, typically within 10-15 seconds after turning on the tap.

Factors affecting instantaneous heating:

Time spent unused can make a small difference. If your unit hasn’t been used for a while, it might take a few extra seconds for the water to reach the desired temperature. But we’re still only talking seconds, not minutes.

Multiple taps running at once can affect performance. If you’ve got multiple taps running at the same time, the water temperature and the flow rate can both be affected. This is one of the trade-offs with instantaneous systems compared to storage tanks.

Flow rate matters too. Instantaneous systems are rated by how many litres per minute they can heat to a certain temperature rise. If the incoming water is particularly cold (winter) or you’re trying to run multiple outlets, you might notice reduced temperature or flow.

How Long Does a Heat Pump Hot Water System Take to Heat Up?

Heat pump hot water systems are becoming increasingly popular thanks to their energy efficiency and government rebates. However, they work differently from traditional systems and generally take longer to heat water.

Heat pumps extract warmth from the surrounding air (even in cooler weather) and use it to heat your water. Think of it like a reverse refrigerator. This process is highly efficient but not particularly fast.

Typical heat pump heating times:

200L tank: 2-4 hours
270L tank: 3-5 hours
315L tank: 4-6 hours

Factors that affect heat pump performance:

Ambient temperature matters more with heat pumps than other systems. They work best when the air temperature is above 10°C. During cold snaps below 5°C, heating times can extend significantly. Sydney’s mild climate is generally well-suited to heat pumps, though winter mornings can slow things down.

Most heat pump systems include an electric booster element for high-demand periods or colder weather. This “boost mode” can speed up heating considerably but does use more energy.

If your heat pump is taking longer than expected, check that the air intake isn’t blocked by debris, leaves, or obstructions. Poor airflow is one of the most common causes of sluggish heat pump performance.

How Long Does a Solar Hot Water System Take to Heat Up?

Solar hot water systems harness the sun’s energy to heat your water, making them one of the most environmentally friendly options available. However, their heating time depends heavily on one factor you can’t control: the weather.

Typical solar heating times:

Sunny day: 3-5 hours to fully heat storage tank
Partly cloudy: 4-6 hours (may not reach full temperature)
Overcast/rainy: Relies on electric or gas booster

Solar systems collect heat through roof-mounted panels or evacuated tubes, which transfer warmth to water stored in an insulated tank. On a good sunny day in Sydney, you can expect easy hot water availability by late afternoon or evening.

Making the most of solar hot water:

Most solar systems include an electric or gas booster for cloudy days or periods of high demand. Without a booster, you might find yourself with lukewarm water after several overcast days in a row.

The orientation of your solar collectors matters too. North-facing panels at the correct angle will capture the most sunlight throughout the year. Shading from trees or neighbouring buildings can significantly reduce performance.

If your solar system isn’t heating as well as it used to, dirty collectors could be the culprit. A layer of dust, bird droppings, or leaf debris can reduce efficiency noticeably. Regular cleaning helps maintain optimal performance.

Recovery Time vs Initial Heating: What’s the Difference?

When we talk about how long a hot water system takes to heat up, we’re actually describing two different scenarios that people often confuse.

Initial heating is how long it takes to heat a completely cold tank from scratch. This happens when you first install a new system, after the power has been off for an extended period, or if you’ve completely drained the tank.

Recovery time is how long it takes to reheat the tank after you’ve used some (but not all) of the hot water. This is what happens after a shower or running the dishwasher.

The good news? Recovery time is almost always faster than initial heating. If you’ve used half the tank’s hot water, your system doesn’t need to heat the entire volume from cold. The remaining hot water mixes with incoming cold water, and the system only needs to bring the overall temperature back up to the set point.

Typical recovery times after moderate use:

System Type	Recovery Time (after 50% use)
Gas storage	15-30 minutes
Electric storage	30-60 minutes
Heat pump	1-2 hours

This is why running out of hot water completely feels like such a long wait. You’re experiencing initial heating time rather than the quicker recovery time you’re used to.

Factors That Influence Hot Water Heating Time

So, you’ve run through the troubleshooting steps and there’s nothing obviously wrong? Maybe you’ve just run into a few of the major factors that impact how quickly your hot water system can heat up. Remember, it’s not always just about patience, but a complex mix of science and system specifics.

System type: If it’s a fully-functioning tankless (or instantaneous) hot water system, that should give you hot water very quickly, within a few seconds. A tank system, though, can take a while for the hot water to reach your tap.

Tank capacity: What is the size of your hot water system? Is it a particularly big one? It should be chock-full of hot water, but if you’re waiting for it to heat up, that’s going to take quite a bit longer.

Energy type: Gas or electric? If electric, it can take longer to heat up than gas. But it’s not going to make a huge difference for instantaneous systems.

Initial water temperature: How cold is the weather out there? If it’s the dead of winter, it’s time to be patient because you’re asking your system to work a lot harder to reach the desired temperature.

Thermostat setting: Your thermostat should be at a fixed temperature, but if you’ve cranked it all up to something particularly hot, that will take longer once you turn that hot tap.

System efficiency: Is your system brand new or quite old? If the latter, expect a longer wait time, or start looking into a repair, some maintenance, or something brand new.

Maintenance history: When was the last time you had a professional out to service your hot water system? Regular maintenance keeps heating times optimal.

Usage patterns: Do you have two or even three showers in quick succession? If so, trying to churn out hot water at the same time could mean seriously extended heating times.

How Weather and Climate Affect Heating Time

Sydney’s climate is generally kind to hot water systems, but seasonal changes can still affect how quickly your water heats up.

Winter considerations:

During colder months, the water entering your system from the mains is noticeably cooler. Instead of starting at around 20°C, incoming water might be closer to 12-15°C on cold mornings. That extra temperature gap means your system has to work harder and longer to reach the target 60°C.

For heat pumps, cold ambient temperatures reduce efficiency. While modern heat pumps can operate in temperatures as low as -10°C, they perform best above 10°C. Sydney winters rarely get that cold, but early morning heating cycles may take longer than midday ones.

Solar systems are most affected by seasonal changes. Shorter daylight hours and lower sun angles in winter mean less energy collection. This is where a well-functioning booster becomes essential.

Summer considerations:

Warmer incoming water temperatures in summer can noticeably speed up heating times. Your system might reach temperature 20-30% faster than in winter simply because it’s starting from a higher baseline.

Heat pumps thrive in warmer weather, often performing at their best efficiency during Sydney summers. Solar systems also benefit from longer days and stronger sunlight, sometimes heating a full tank by early afternoon.

How to Reduce Hot Water Heating Time

While you can’t fundamentally change how fast your system heats water, there are practical steps to ensure it’s working at peak efficiency.

Maintain consistent thermostat settings. Constantly adjusting your thermostat makes the system work harder and can actually increase overall heating time. Set it to the recommended 60°C for storage systems and leave it there.

Insulate your hot water pipes. Heat loss through uninsulated pipes means your system works harder, and hot water takes longer to reach your taps. Pipe insulation is inexpensive and can make a noticeable difference, especially for systems located far from bathrooms.

Schedule your hot water use. If you have an off-peak electric system, it heats overnight and may not fully recover during the day. Staggering showers rather than having everyone wash within the same hour gives the system time to recover between uses.

Keep up with regular maintenance. Sediment buildup, failing elements, and worn components all slow down heating. Annual servicing keeps your system running efficiently and can identify problems before they become major issues.

Consider a timer for heat pumps. Running your heat pump during the warmest part of the day (typically 11am-3pm) means it’s working in optimal conditions and will heat faster than during cold mornings or evenings.

Take shorter showers. It sounds obvious, but reducing hot water consumption means less recovery time needed between uses. Even cutting a few minutes off each shower can make a difference for larger households.

When Is Your Hot Water System Taking Too Long?

It’s one thing to know the typical heating times, but how do you know when your system is genuinely underperforming? Here are some benchmarks that suggest something might be wrong:

Your system is taking too long if:

An electric storage tank takes more than 4 hours to heat from cold
A gas storage tank takes more than 90 minutes to heat from cold
An instantaneous system takes more than 30 seconds to deliver hot water
A heat pump takes more than 8 hours in mild weather
Recovery time has noticeably increased compared to when the system was new
You’re running out of hot water more frequently than usual

Warning signs that indicate a problem:

Rusty or discoloured hot water
Unusual noises like banging, popping, or rumbling
Inconsistent temperatures (hot then cold then hot again)
Significantly higher energy bills without increased usage
Visible leaks around the unit
Pilot light that won’t stay lit (gas systems)

If you’re experiencing any of these alongside slow heating, it’s worth having your system inspected. Sometimes a simple repair like replacing a heating element or flushing sediment can restore normal performance. Other times, an ageing system may simply be reaching the end of its efficient lifespan.

Understanding First Hour Rating

When shopping for a new hot water system, you might come across something called the “first hour rating.” This is actually one of the most useful specifications for understanding real-world performance.

The first hour rating tells you how many litres of hot water the system can deliver in the first hour of use, starting with a full tank at temperature. It takes into account both the stored hot water and the system’s ability to heat more water during that hour.

For example, a 160L electric tank might have a first hour rating of 180L. That means even though the tank only holds 160L, it can recover quickly enough to deliver an extra 20L during that first hour of heavy use.

This matters because it reflects actual usability better than tank size alone. A smaller tank with excellent recovery might outperform a larger tank with slower heating for households with concentrated morning usage.

When sizing a new system, think about your peak demand period. If everyone showers, runs the dishwasher, and does laundry within a two-hour window each morning, you need a system with a first hour rating that can handle that demand.

Frequently Asked Questions

How long does a gas water heater take to heat up compared to electric?

Gas water heaters typically heat about twice as fast as electric ones. A 135L gas tank takes around 30-45 minutes to heat from cold, while an equivalent electric tank might take 2-3 hours. The difference comes down to how efficiently gas combustion transfers heat compared to electric elements.

Why is my hot water taking so long to heat up suddenly?

If your system used to heat quickly but has slowed down, common culprits include sediment buildup in the tank, a failing heating element (electric systems), burner issues (gas systems), or thermostat problems. It could also indicate your system is reaching the end of its lifespan.

Can I make my hot water heat up faster?

You can’t change the fundamental heating speed of your system, but you can optimise it. Keep up with regular maintenance, insulate your pipes, avoid excessive thermostat adjustments, and ensure nothing is blocking airflow for heat pumps. Upgrading to a gas system or instantaneous unit will provide faster heating if speed is a priority.

How long should I wait for hot water from an instantaneous system?

Instantaneous systems should deliver hot water within 5-15 seconds of turning on the tap. If you’re waiting longer than 30 seconds, there may be an issue with the unit, the gas/power supply, or the flow rate may be too low to activate the heating.

Is it normal for my heat pump to take 4-5 hours to heat?

Yes, this is within normal range for heat pumps, especially larger tanks or during cooler weather. Heat pumps prioritise efficiency over speed. If you need faster heating occasionally, most units have a boost mode that uses a standard electric element.

Does the temperature outside affect how long my hot water takes to heat?

Yes, particularly for heat pumps and solar systems which rely on environmental conditions. Even for traditional gas and electric systems, colder incoming water temperatures during winter mean longer heating times. The difference can be 20-30% between summer and winter.